In diverse types of mechanisms for filling devices of various classes, it is necessary to have tanks of liquid at a determined height so that the liquid reaches the filling mechanisms at suitable manometric pressure. For the same reason and in accordance with the diverse physical characteristics of the liquids, this must vary. This causes the need for constructing support towers for the tanks at heights which are generally inconvenient, and with the requirement to vary such heights according to need. This requires the installation of regulating devices which make the equipment both more complicated and expensive.
In another sphere, it is already known that in liquid-feeding devices for filling mechanisms for diverse types of utilization devices a pump is employed. However, deficiencies are observed with regard to the pressure conditions, i.e. to the establishment of differences of pressure of the liquid which is being fed. The pressure of the liquid must not vary but should be kept constant with absolute precision. Generally, conventional pumps do not guarantee the non-return of the liquid; they are not one-directional; they are not even leakproof, so that, when the pump is stopped, the liquid can flow in one direction or the other according to the manometric pressure of the liquid.